Smooth 3D bezier curves with implicit control points

This code can be used to draw 3D cubic splines by only entering the points through which the spline should pass.

In other words, smooth curves can be drawn by simply defining occasional points through which the curve should pass.

Bezier control points are calculated automatically using the Hobby's algorithm (1986), which allows a slope and "tension" of the spline at each point to be specified explicitly if desired.